March 5, 2008

  • underwater vision

    So, I actually learned something interesting today. At least, I think it's interesting... so I thought I'd share. Underwater vision... I haven't really thought too much about it before. I just figured, sure, it's blurry because you are underwater and the water is getting in your eyes and because, well, it hurts. That was the extent of it for me. Here's the real deal: our eyes, obviously, are adapted to seeing in air, which has a refractive index (n) of about 1.0 (refractive index, as in, how much the light bends when it goes from one medium to the next)... so normally, light goes from n=1.0 to n=1.38 as it enters the fluid between the cornea and the lens from the air. Soooo... when you are underwater... the n of water is about 1.33... very close to the liquid in the eye. So close, in fact, that the cornea virtually loses its ability to bend the light... so the image focuses way behind the retina as if you were really farsighted, making it blurry! But, here's the kicker: if you are really nearsighted and you swim underwater, you could potentially see clearly because your nearsightedness will compensate for the lack of refraction on the cornea.

    So, here's a thought... in the whole scheme of things, you never know... maybe nearsighted people are going to win out in the evolutionary battle we call life and one day people will live underwater and see clearly. Maybe it will be one of nature's solutions for the whole global warming thing...